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Summary In seed plants, 1‐aminocyclopropane‐1‐carboxylic acid (ACC) is the precursor of the plant hormone ethylene but also has ethylene‐independent signaling roles. Nonseed plants produce ACC but do not efficiently convert it to ethylene. InArabidopsis thaliana, ACC is transported by amino acid transporters, LYSINE HISTIDINE TRANSPORTER 1 (LHT1) and LHT2. In nonseed plants,LHThomologs have been uncharacterized.Here, we isolated an ACC‐insensitive mutant (Mpain) that is defective in ACC uptake in the liverwortMarchantia polymorpha. Mpaincontained a frameshift mutation (1 bp deletion) in the MpLHT1coding sequence, and was complemented by expression of a wild‐type MpLHT1transgene. Additionally, ACC insensitivity was re‐created in CRISPR/Cas9‐Mplht1knockout mutants. We found that MpLHT1 can also transportl‐hydroxyproline andl‐histidine.We examined the physiological functions of MpLHT1in vegetative growth and reproduction based on mutant phenotypes. Mpainand Mplht1plants were smaller and developed fewer gemmae cups compared to wild‐type plants. Mplht1mutants also had reduced fertility, and archegoniophores displayed early senescence.These findings reveal that MpLHT1 serves as an ACC and amino acid transporter inM. polymorphaand has diverse physiological functions. We propose that MpLHT1 contributes to homeostasis of ACC and other amino acids inM. polymorphagrowth and reproduction.